The architecture supporting Policy and Charging Control (PCC) functionality is illustrated in FIG. 1 and disclosed in 3GPP TS 23.203 V13.4.0 that specifies the PCC functionality for Evolved 3GPP Packet Switched domain, including both 3GPP accesses (GERAN/UTRAN/E-UTRAN) and Non-3GPP accesses. For the purpose of the embodiments further discussed, the PCC architecture includes a Policy and Charging Rules Function (PCRF), a Policy and Charging Enforcement Function (PCEF) and an Online Charging System (OCS) to allow charging decisions. The 3GPP TS 23.203 discloses a Gx reference point (interface) between the PCRF and the PCEF, and a Gy reference point (interface) between the OCS and the PCEF.
The PCRF is in charge of policy control decision and flow based charging control, and provides network control for service data flow detection, gating, quality of service (QoS) and flow based charging towards the PCEF by holding policies and providing PCC rules to the PCEF per service data flow basis for enforcement of such policies. That is, with the PCC rules, the PCRF instructs the PCEF on the treatment of each service data flow.
The PCEF encompasses service data flow detection, policy enforcement and flow based charging functionalities by enforcing the PCC rules received from the PCRF.
In particular, the PCEF may be located at e.g. a gateway GPRS support node (GGSN) in a general packet radio service (GPRS) core network. The GPRS core network allows 2G, 3G and WCDMA mobile networks to transmit IP packets to external networks such as the Internet. Moreover, the PCEF may also be located at e.g. a packet data network gateway (PGW) in an evolved packet system (EPS) network. The PGW, which may also be abbreviated as PDN GW, is the point of interconnect between the evolved packet core (EPC) and the external IP networks. Furthermore, the PCEF may also be located at e.g. a packet data gateway (PDG) for connecting an untrusted WLAN network with a 3GPP network. In this scenario, the PDG may be a gateway to a specific packet data network, such as the internet or an operator service network.
In some use cases, policy control and/or charging decisions, such as QoS modification or charging rate change may depend on whether a user equipment (UE) is located inside or outside a specific area of interest, i.e. a Presence Reporting Area, and especially on whether the UE enters or leaves that specific area of interest.
3GPP Rel-12 standardized the concept of Presence Reporting Area (PRA) and a mechanism to report to PCRF and OCS when a UE enters or leaves a specific PRA, identified by a PRA identifier (PRA-id). PRAs are supposed to help the operator to provide services when a UE enters or leaves an area of interest, e.g. provide free quota at home or at a coffee shop. Only one PRA-id can be provided by PCRF, through the PCEF, to a Mobility Management Entity (MME) or serving GPRS support node (SGSN) per IP-CAN session to reduce signalling. Both the PCRF and OCS can activate reporting when UE enters or leaves a PRA-id.
In this respect, 3GPP Rel-13 defines that the PCRF provides the PRA-id at IP-CAN session establishment, without prior knowledge of whether the PRA-id includes an area under the coverage of the MME/SGSN where the UE is attached. 3GPP TS 23.401 V13.4.0 defines that the source MME/SGSN provides the PRA-id at mobility and handover scenarios to a target MME/SGSN. The target MME/SGSN checks the E-UTRAN cell global identifier (ECGI) or cell global identity (CGI), hereinafter ECGI/CGI, where the UE is located versus the ECGI/CGIs defined as part of the PRA-id and then reports if the UE is inside or outside the PRA-id.
Whilst currently the PCRF just provides one PRA-id to the MME/SGSN, 3GPP Rel-14 is studying extensions to allow PCRF to provide multiple PRA-ids per IP-CAN session to the PCEF and the PCEF towards the MME/SGSN. More precisely, 3GPP TR 23.710 V0.1.0 defines a key issue to study how to control the number of PRA-ids to be monitored, and which are provided by PCRF via the PCEF to the MME/SGSN. The reason is that a large number of PRA-ids provided per IP-CAN session may cause too high load in MME/SGSN.
The key issue in this 3GPP TR 23.710 aims to provide a solution to support efficient resource handling in MME and SGSN. That means that the MME/SGSN will allow only a limited number of PRAs active per IP-CAN session. Provisioning of PRA-ids active in PCRF for an IP-CAN session would lead to inconsistent information in MME/SGSN and in PCRF and potential lack of reporting to PCRF.
In view of 3GPP TS 23.401 V13.4.0, at mobility from source to target MME/SGSN, reporting that a UE enters or leaves a certain PRA-id would lead to inconsistencies between the list of PRA-ids active for the IP-CAN session in the PCRF and the PRAs that are active in the MME/SGSN to fulfil the requirement for efficient resource handling.
Moreover, in view of 3GPP TS 23.401 V13.4.0, at mobility from an MME/SGSN compliant with 3GPP Rel-12 to another MME/SGSN compliant with 3GPP Rel-14, the target MME/SGSN will only receive one PRA from the old MME/SGSN and it will not know about the other PRAs that apply to the IP-CAN session,